Let's play with a little bit of symbolic logic. Near the end of the article the founders talk say, if your life falls apart then you can't count that as success. Well, you need a little bit of revenue for your life to not fall apart. We can distill that down to:

  If no revenue, then no success

The contrapositive of which is:

  If success, then revenue

Then given our previous theorem:

  If (Users and Hard Work) then Success.

Causality is commutative, so we can just substitute our earlier result:

  If (Users and Hard Work) then Revenue.

Thus we get Revenue in to that equation. This ought to work, at least in theory :)